In specific parts of the country, primarily urban areas where concentrations of ozone in the summer or carbon monoxide in the winter exceed established air-quality standards, the Clean Air Act Amendments of 1990 mandate compounds that add oxygen (referred to as oxygenates) be added either seasonally or year round to gasoline. Such oxygenates increase the octane of the gasoline and improve air quality.
Even though oxygenates are mandated primarily in urban areas, it is estimated that oxygenates are added to more than 30 percent of the gasoline sold in the United States presently. By the end of this decade, the Oxygenated Fuels Association estimates that oxygenates will be added to 70 percent of the gasoline sold in this country.
Methyl tertiary butyl ether (MTBE) comprises one popular oxygenate permitted in unleaded gasoline up to a level of 15 percent. MTBE is a volatile organic compound (VOC) made from methanol and derived from natural gas. As one of the primary ingredients in reformulated gasolines, production of MTBE in 1993 ranked second among all organic chemicals manufactured. In 1993, 24 billion pounds of MTBE, worth about $3 billion, were produced. MTBE is commonly used because of its low cost, ease of production, and favorable transfer and blending characteristics.
Although MTBE comprises a popular, cost effective clean-burning oxygenate, with high octane and "relatively low" volatility, the U.S. Environmental Protection Agency (EPA) has tentatively classified the substance as a possible human carcinogen. Hence, other oxygenates, such as TAME (tertiary amyl methyl ether) are receiving serious development and consideration. Ethanol and ETBE (ethyl tertiary butyl ether) may compete for the consumer market. Environmental, health, economic and even political factors will probably affect the success and market share of competing products in this area of "finished product" hydrocarbons, gas additives and/or blended fuels.
As of this date, MTBE is representative of a growing inventory of "finished product" fluids that are manufactured in such quantities as to require storage in large tanks and that have either a relatively low boiling point (as compared to gasoline or crude, for instance) or a low auto-ignition temperature, or possibly both. The boiling point of MTBE is approximately 133.degree. F. MTBE's auto-ignition temperature is approximately 450.degree. F. The auto-ignition temperature of gasoline, by comparison, is approximately 900.degree. F.
The increased production of and need for "finished product" hydrocarbons--blended fuels, MTBE, TAME and the like--increases the danger and risks of handling fires involving such fluids. Produced and consumed in large volumes, the fluids must be stored in large tanks. The present inventors have discovered that existing systems for extinguishing hydrocarbon tank fires, including systems for the management of foam attack, should be improved to cover the difficult and dangerous situations that could arise with MTBE and the like tank fires.
The present invention discloses improved fire fighting systems with steps that are beneficial when addressing fires of low boiling point and/or a low auto-ignition point fluids. The invention includes steps for improving foam attack techniques. The present invention also teaches incorporating improved steps and improved foam attacks into systems using nozzles stored on or around a tank rim as well as distant from the tank.